4 slot is the best for x299 boards.. If you go directly to the nvlink page, it will show proper spacing.

On x299, the 4 slot spacing is typically the best, especially with 3 slot cards. This will give an extra bit of breathing room of the card.

3 slot is best for z390 style boards.

startekselva
whats the distance between  PE1 and PE4 in dark im planning to buy water loop for the gpu need support
 

• 2Way use for 4 cm
• 2Way use for 6 cm
• 2Way use for 8 cm
• whats the distance 
  

80mm.